function sys=plant(t,x,k)
sys=zeros(2,1);

alpha=3;beta=9;
x1=x(1);y1=x(2);
if k<1000
    fi=0.2;
else
    fi=-0.2;
end

sys(1)=y1-alpha*sqrt(abs(x1))*sign(x1);
sys(2)=fi-beta*sign(x1);
end